A method and system for estimating velocity of an aircraft is provided. The method comprises transmitting a beam toward a surface from the aircraft using a Doppler beam sharpened radar altimeter, receiving a plurality of reflected signals that correspond to portions of the transmitted beam that are reflected by the surface, and forming a plurality of Doppler beams by filtering the received signals. A complex-valued array of range bin is computed with respect to frequency of the Doppler beams from at least one antenna aperture of the radar altimeter, and a range for each of the Doppler beams is estimated. A velocity vector magnitude for the aircraft is estimated by a curve fit of the range with respect to the frequency of the Doppler beams.
Legal claims defining the scope of protection, as filed with the USPTO.
1. A method for estimating velocity of an aircraft, the method comprising: transmitting a beam toward a surface from the aircraft using a Doppler beam sharpened radar altimeter; receiving a plurality of reflected signals that correspond to portions of the transmitted beam that are reflected by the surface; forming a plurality of Doppler beams by filtering the received signals; computing a complex-valued array of range bin with respect to frequency of the Doppler beams from at least one antenna aperture of the radar altimeter; estimating a range for each of the Doppler beams; and estimating a velocity vector magnitude for the aircraft by a curve fit of the range with respect to the frequency of the Doppler beams.
2. The method of claim 1 , wherein the estimated velocity vector magnitude comprises a real-time estimate of velocity of the aircraft over water.
3. The method of claim 1 , further comprising determining an estimated uncertainty based on a range variation across the Doppler beams.
4. The method of claim 1 , wherein an angle above horizon is used to calculate a vertical velocity.
5. The method of claim 1 , further comprising: estimating interferometric phase angles for each of the Doppler beams using at least two antenna apertures of the radar altimeter; and estimating a velocity vector horizontal direction of the aircraft based on the interferometric phase angles of the Doppler beams.
6. The method of claim 1 , further comprising: estimating interferometric phase angles for each of the Doppler beams using at least two antenna apertures of the radar altimeter; and computing an attitude of the aircraft based on the interferometric phase angles of the Doppler beams.
7. The method of claim 1 , further comprising correcting the velocity vector magnitude based on a terrain slope of the surface.
8. The method of claim 5 , further comprising correcting the velocity vector horizontal direction based on a terrain slope of the surface.
9. The method of claim 6 , further comprising correcting the attitude of the aircraft based on a terrain slope of the surface.
10. The method of claim 1 , further comprising estimating an angle above horizon for the aircraft by a curve fit of the range with respect to the frequency of the Doppler beams.
11. A computer program product, comprising: a non-transitory computer readable medium having instructions stored thereon executable by a processor to perform a method for estimating velocity of an aircraft according to claim 1 .
12. A system for estimating velocity of an aircraft, the system comprising: at least one processor in the aircraft; and a processor readable medium having instructions stored thereon executable by the processor to: transmit a beam toward a surface from the aircraft using a Doppler beam sharpened radar altimeter; receive a plurality of reflected signals that correspond to portions of the transmitted beam that are reflected by the surface; form a plurality of Doppler beams by filtering the received signals; compute a complex-valued array of range bin with respect to frequency of the Doppler beams from at least one antenna aperture of the radar altimeter; estimate a range for each of the Doppler beams; and estimate a velocity vector magnitude for the aircraft by a curve fit of the range with respect to the frequency of the Doppler beams.
13. The system of claim 12 , wherein the processor readable medium has further instructions stored thereon executable by the processor to: estimate interferometric phase angles for each of the Doppler beams using at least two antenna apertures of the radar altimeter; and estimate a velocity vector horizontal direction of the aircraft based on the interferometric phase angles of the Doppler beams.
14. The system of claim 12 , wherein the processor readable medium has further instructions stored thereon executable by the processor to: estimate interferometric phase angles for each of the Doppler beams using at least two antenna apertures of the radar altimeter; and compute an attitude of the aircraft based on the interferometric phase angles of the Doppler beams.
15. The system of claim 12 , wherein the processor readable medium has further instructions stored thereon executable by the processor to correct the velocity vector magnitude based on a terrain slope of the surface.
16. A method for estimating attitude of an aircraft, the method comprising: transmitting a beam toward a surface from the aircraft using a radar altimeter; receiving a plurality of reflected signals that correspond to portions of the transmitted beam that are reflected by the surface; estimating a range to a closest point on the surface; computing at least one interferometric phase angle between at least two antenna apertures of the radar altimeter at the range to the closest point on the surface; and estimating at least one component of aircraft attitude using the at least one interferometric phase angle.
17. The method of claim 16 , wherein the at least one component of aircraft attitude includes a pitch angle or a roll angle.
18. The method in claim 16 , further comprising correcting the estimated at least one component of aircraft attitude based on a terrain slope of the surface.
19. A computer program product, comprising: a non-transitory computer readable medium having instructions stored thereon executable by a processor to perform a method for estimating attitude of an aircraft according to claim 16 .
Cooperative Patent Classification codes for this invention. Click any code to explore related patents in that topic.
July 28, 2015
June 26, 2018
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